Almquist et al., "Synthesis and Biological Activity of a Ketomethylene Analogue of a Tripeptide Inhibitor of Angiotensin Converting Enzyme", J. Med. Chem., 1980, 23, 1392-1398, disclose the ketomethylene compound of the formula ##STR2##
Meyer et al., "Novel Synthesis of (S)-1-[5-(Benzoylamino)-1,4-dioxo-6-phenylhexyl]-L-proline and Analogues: Potent Angiotensin Converting Enzyme Inhibitors", J. Med. Chem., 1981, 24, 964-969, disclose the synthesis and activity of compounds of the formula ##STR3##
Meyer et al., "Angiotensin Converting Enzyme Inhibitors: Modifications Of A Tripeptide Analogue", J. Med. Chem., 1982, 25, 996-999, disclose the synthesis and activity of compounds of the formula ##STR4## wherein X can be NH and R can be L-proline.
Almquist et al. in U.S. Pat. No. 4,329,473 disclose oxoalkanoic acid derivatives of L-proline as angiotensin converting enzyme inhibitors.
Gravestock et al. in European Patent Application No. 45161 disclose hypotensive compounds of the formula EQU R.sup.1 --Y--NR.sup.2 --CHR.sup.3 --X--CHR.sup.11 --CHR.sup.4 --CO--NR.sup.5 --CR.sup.6 R.sup.16 --Q--R.sup.10.
Mercaptoacyl derivatives of proline and substituted prolines are known to be useful hypotensive agents due to their angiotensin converting enzyme inhibition activity. Ondetti, et al. in U.S. Pat. No. 4,105,776 disclose such compounds wherein the proline ring is unsubstituted or substituted by an alkyl or hydroxy group. Ondetti, et al. in U.S. Pat. No. 4,154,935 disclose such compounds wherein the proline ring is substituted with one or more halogens. Ondetti, et al. in U.S. Pat. No. 4,316,906 disclose such compounds wherein the proline ring is substituted by various ethers and thioethers. Krapcho in U.S. Pat. No. 4,217,359 disclose such compounds wherein the proline ring has a carbamoyloxy substituent. Krapcho in U.S. Pat. No. 4,311,697 discloses compounds wherein the proline ring has a diether, dithioether, ketal or thioketal substituent in the 4-position. Krapcho in U.S. Pat. No. 4,316,905 discloses such compounds wherein the proline ring has a cycloalkyl, phenyl, or phenyl-lower alkylene substituent. Ondetti, et al. in U.S. Pat. No. 4,234,489 disclose such compounds wherein the proline has a keto substituent in the 5-position. Krapcho, et al. in U.S. Pat. No. 4,310,461 disclose such compounds wherein the proline has an imido, amido, or amino substituent in the 4-position. Iwao, et al. in U.K. Patent Application No. 2,027,025 disclose such compounds wherein the proline has an aromatic substituent in the 5-position.
Mercaptoacyl derivatives of 3,4-dehydroproline are disclosed as angiotensin converting enzyme inhibitors by Ondetti in U.S. Pat. No. 4,129,566. Mercaptoacyl derivatives of thiazolidinecarboxylic acid and substituted thiazolidinecarboxylic acid are disclosed as angiotensin converting enzyme inhibitors by Ondetti in U.S. Pat. No. 4,192,878 and by Yoshitomo Pharmaceutical Ind. in Belgium Pat. No. 868,532.
Mercaptoacyl derivatives of dihydroisoindole carboxylic acids and tetrahydroisoquinoline carboxylic acids are disclosed as being useful hypotensive agents by Ondetti et al., in U.S. Ser. No. 69,031, filed Aug. 23, 1979. These mercaptoacyl tetrahydroisoquinoline compounds are also disclosed by Portlock in U.K. Application No. 2,048,863 and by Hayashi et al. in U.S. Pat. No. 4,256,751.
Various carboxyalkyl dipeptide angiotensin converting enzyme inhibitors are disclosed by Patchett et al. in European Patent Application No. 12,401 and by Harris et al. in U.S. Pat. No. 4,374,829.